BRCA1 and breast cancer: Mutations in BRCA1 predispose women to a higher lifetime risk of breast and ovarian cancer.29 BRCA1 is implicated in mammary epithelial cell differentiation and its deficiency is often associated with basal-like breast cancer subtype.30 Although it has been reported that BRCA1 imposes its tumour suppressive role by regulating DNA damage repair and cell cycle checkpoint, the exact reason whereby BRCA1 deficiency or mutation causes more aggressive breast cancer phenotype remains largely unknown.